# JEE Main & Advanced Physics One Dimensional Motion Position

Position

Category : JEE Main & Advanced

Any object is situated at point O and three observers from three different places are looking at same object, then all three observers will have different observations about the position of point O and no one will be wrong. Because they are observing the object from different positions.

Observer 'A' says : Point O is 3 m away in west direction.

Observer 'B' says : Point O is 4 m away in south direction.

Observer 'C' says : Point O is 5 m away in east direction.

Therefore position of any point is completely expressed by two factors: Its distance from the observer and its direction with respect to observer.

That is why position is characterised by a vector known as position vector.

Consider a point P in xy plane and its coordinates are (x, y). Then position vector $(\vec{r})$ of point will be $x\hat{i}+y\hat{j}$ and if the point P is in space and its coordinates are (x, y, z) then position vector can be expressed as $\vec{r}=x\hat{i}+y\hat{j}+z\hat{k}.$

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